Any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material forms a part of the prior art base or the common general knowledge in the relevant art in the United States of America, Australia, or elsewhere, on or before the priority date of the disclosure herein.
Unless stated otherwise, throughout the ensuing description, the expression “gas(es)” refers to any suitable gas, or mixture of gases and/or gaseous elements or agents, that can be monitored using gas flow indicator apparatus of the present invention. In the context of medical or other respiratory applications of gas flow indicator apparatus of the present invention, “gas” refers to any suitable breathing gas(es) which will generally be oxygen, or a mixture of oxygen and one or more inert gases and/or pharmacological agents, and/or air which of course is a combination of oxygen and other gases/elements. Similarly, the expressions “gas delivery device(s)” or “gas delivery system(s)” refer to any suitable device(s), system(s), and/or conduit(s) for supplying gas(es) to, or at, a desired location. In the context of medical or other respiratory applications of the gas flow indicator apparatus of the present invention, “gas delivery device(s)” or “gas delivery system(s)” refer to any suitable breathing apparatus, system and/or supply conduit(s), etc., for introducing or supplying gas(es) into/to an individual's airway. For example, for individuals breathing spontaneously suitable apparatus, systems, etc., may include, but are not limited to: face masks; mouth pieces; nasal cannulas; and/or, gas supply conduit(s). Whereas for non-spontaneous breathing applications suitable apparatus, systems, etc., may include, but are not limited to; manual resuscitator devices, such as bag valve masks; endotracheal tubes; and/or, gas supply conduit(s). A skilled person will appreciate many such devices, systems, conduits, etc., alternatives, and/or variations thereof, and hence the present invention should be construed as including within its scope any suitable means of supplying gas to an individual's airway. Finally, the definitions of the expressions hereinbefore described are only provided for assistance in understanding the nature of the invention, and more particularly, the preferred embodiments of the invention as hereinafter described. Such definitions, where provided, are merely examples of what the expressions refer to, and hence, are not intended to limit the scope of the invention in any way.
Supplemental gas is widely used in the medical field. For example, supplemental oxygen is used to assist or maintain safe normal blood levels of oxygen within a patient. The duration of supply of supplemental oxygen varies depending on the condition of the patient and/or the particular circumstance necessitating the administration of the supplemental oxygen supply. Common scenarios include patients having a cardiorespiratory disease or dysfunction and/or surgical/anaesthetic interventions that mandate supplementation of atmospheric air with higher concentrations of inspired oxygen in order to achieve normal oxygen tensions in the patient's blood. Failure to deliver this supplemental oxygen can lead to risk of reduced arterial oxygen tension which, if uncorrected, contributes directly to increased morbidity and mortality.
Failure of supplemental gas delivery is an acknowledged and feared system risk in the hospital environment. To safeguard from this, more often than not there are multilevel complex alarms and flow sensors within the hospital's in-built gas piping circuitry, and/or at gas supply outlets provided throughout hospital facilities. In addition, anaesthetic machines, intensive care ventilators, or the likes, have mandatory flow sensors engineered into their design to detect and alert of gas supply failure.
Although most hospital's gas supply systems, from source to supply outlet, are generally monitored, as are complex anaesthetic machines and/or ventilators, the most commonly used, and often most simple, gas delivery devices, systems and/or conduits, are not provided with any gas flow indicator apparatus, or at least any effective or useful gas flow indicator apparatus. Hence, use of such gas delivery devices, systems, etc., can lead to supplementary gas delivery or supply failure going unnoticed. This risk is magnified in situations involving gas supply from portable gas tanks or cylinders.
One of the most commonly used gas delivery devices for spontaneously breathing patients is the gas delivery mask, or oxygen mask. Sometimes called the “Hudson Mask”, with reference to the early mask innovations of the Hudson Company, most such masks are made of a clear plastics material and include a body, which is either resilient or rigid, that is sized to seat over the nose and mouth of a patient. With conventional mask designs, gas is introduced through a gas inlet, and expiratory gases are vented from either around the side of the mask and/or through appropriately placed ventilation apertures. Gas is supplied to the gas inlet from a gas supply source, commonly by way of a length of clear plastic conduit. The gas supply source may be an in-built hospital supply source, or a gas tank or cylinder.
Oxygen masks are designed to increase a patient's inspired fraction of oxygen from about 21% to about 40%. The oxygen flow rate required to achieve this is about 6 liters per minute (“6 L/min”). When oxygen flow into the mask fails, not only is the desired ˜40% inspired oxygen concentration not achieved, but of greater concern, the patient re-breathes their expired gases which cannot be satisfactorily replenished by entrainment of air around the side of the mask, ultimately leading to the inspiration of a hypoxic gas mixture (oxygen concentration of less than 21%). As oxygen masks are not presently provided with any visual indicator confirming the presence of oxygen flow into the mask, or in the oxygen supply conduit proximate the mask, complete lack of oxygen flow or insufficient flow (i.e. less than 6 L/min) is not inherently obvious to a medical practitioner, carer, or to the patient themselves, such as in circumstances where individual's administer their own supplemental oxygen supply. A visual inspection of the oxygen delivery system (e.g. conduit and mask), distal to the oxygen supply outlet or source, will not generally indicate whether oxygen is or isn't flowing. For this reason, often medical practitioners, etc., find themselves having to use their ears as a means of identifying oxygen flow. Although putting ones ear at or near a mask, etc., may sometimes identify that gas is flowing, the medical practitioner still has no way of knowing whether the desired flow rate of oxygen (i.e. about 6 L/min) is present in or at the mask.
For non-spontaneously breathing patients, one of the most commonly used manual resuscitator gas delivery devices is the bag valve mask or “BVM”. Sometimes called the “AMBU” bag or mask, with reference to the proprietary name appointed by the inventors' of the original BVM, such devices consist of a flexible air chamber (the “bag”) attached to a face mask or endotracheal tube via a shutter valve. When the mask is properly applied to a patient (or endotracheal tube is correctly inserted into the patients trachea) and the “bag” is squeezed, the device forces air into the patient's lungs. When the bag is released, it self-inflates from its supply end, drawing in either ambient air or oxygen supplied by an oxygen supply source, while also allowing the patient's lungs to deflate to the ambient environment (and not the “bag”) by way of a one-way expired air valve. The BVM generally includes two inlet ports for drawing in ambient air or oxygen. When available, oxygen is supplied to one of the inlet ports from a gas supply source, commonly by way of a length of clear plastic conduit. The gas supply source may be an in-built hospital supply source, or a gas tank or cylinder. The other inlet port can then be used to draw in ambient air, or to connect a reservoir for catching unused oxygen between compressions of the “bag”. In case oxygen flow is not sufficient to fill the “bag”, the reservoir generally includes a one-way valve for drawing in ambient air to ensure that the BVM continues to supply at least ambient air to the patient.
BVM's are designed to deliver up to 100% inspired oxygen to a patient. With a loss of supplemental oxygen supply into the “bag”, the BVM will continue to entrain ambient air (with an oxygen concentration of about 21%) with which to ventilate the patient. However, patient's requiring the use of such manual resuscitator devices often have severely compromised respiratory function, which means that they require much higher inspired oxygen concentrations than that of ambient air. Therefore any loss of supplemental oxygen supply can have catastrophic sequelae if undiagnosed. Like in the case of the common oxygen mask described above, loss of oxygen supply to a BVM can be, and often is, missed as there is presently no visual flow indicator provided at or proximate the BVM confirming supplemental oxygen inflow. Again, although the presence of a sound may indicate that gas is flowing, the medical practitioner still has no way of knowing whether the required flow rate of oxygen is present at the BVM.
Often gas tanks or cylinders are used to supply oxygen to masks or BVM's, most commonly in emergency, perioperative, critical care or transport scenarios. While some cylinders do have ball-type flow indicators at their supply outlets, such cylinders are often placed in visually obscured positions (e.g. under a patient's bed or transportation trolley), or placed side-ways rendering the ball-type flow indicators inaccurate. Additionally, most cylinders do not have alarms in the event of cylinder oxygen supply running empty during use to indicate oxygen supply failure. Even more concerning is that newer designs of oxygen cylinders commonly no longer have ball-type or any flow indicator incorporated into their design. Hence, failure of supplemental gas supply to gas delivery devices or systems is a real and likely problem.
It would be desirable to overcome or alleviate one or more of the aforesaid problems associated with the use of known gas delivery devices, systems, and/or conduits, more particularly, breathing gas delivery devices, systems, and/or conduits, or at least to provide a useful alternative.